The shock wave surrounding the tragic death of robin Williams continues to reverberate as new details paint a heartbreaking picture about the dark side of the actor who brought so much joy to so many fans. On screen, his performances were explosive, energetic and wildly inventive. But robin Williams' brilliance in front of the camera concealed a private sadness. Tonight, the last moments of a legend. It's "The life and death of robin Williams." I miss him. And I'm sure you guys do, too. What a gift he was to all of us. It's just shocking how fragile life is. I was a kid when it was the first time I saw an actual human being be as funny as bugs bunny. Reporter: As Hollywood mourns the death of one of its brightest stars, new details confirming the sad truth about how Williams died. The preliminary results of the forensic examination revealed supporting physical signs that Mr. Williams' life ended from asphyxia due to hanging. Reporter: The actor apparently hung himself with a belt. But that wasn't all they found. The inside of Mr. Williams left wrist had several acute, superficial transverse cuts. A pocket knife was located in close proximity to Mr. Williams. Reporter: His wife told police she last saw her husband about 10:30 Sunday night. But the couple slept in separate beds. Mr. Williams was last seen by his wife at approximately 10:30 August 10th, when she retired for the evening in a room in the home. Reporter: When she woke up the next morning, she didn't see him. At approximately 10:30 A.M., on August 11th, 2014, Mr. Williams' life left the home, believing Mr. Williams to still be asleep. Reporter: Just before noon, after Williams failed to answer the door, his assistant grew concerned. At that time, the personal assistant was able to gain access to Mr. Williams' bedroom. And entered the bedroom to find Mr. Williams, clothed, in a seated position, unresponsive. Reporter: And called 911. Apparent suicide, attempt from hanging. Police respond? Affirmed. Reporter: Had Williams been drinking that night? After his repeated struggles with alcohol? We won't know for a few weeks. But at today's press conference, the discussion of a note raised eyebr eyebrows. We're not discussing a note as the investigation is ongoing. And that will be discussed at a future time. Reporter: Williams was battling severe depression. As many as one in every ten Americans suffer from depression. The reason we misunderstand depression so much is that you can't show me depression on an X ray. You can't show me a court of depression. Reporter: To the outside world, Williams was the hilarious -- Ladies, how about this? Instead of breast implants, speakers. Wouldn't that be cool? Reporter: Larger than life. Is this fun? Reporter: And wholly original comedian. We're going to play Lizzie Borden. Reporter: Who made others laugh. His depression and substance abuse was something he struggled with for years. He checked into rehab most recently last month. This is what we call a dual diagnosis scenario. You have someone dealing with the struggles of addiction through the years. And you put depression on top of that. And the interaction between the two is multiplicative. I'm on my way to Dublin. Reporter: He was brutally honest about his fight for sobriety. In his sandup routine. You will violate your standards quicker than you can lower them. Reporter: And in candid interviews, like this one with Diane sawyer, in 2006, after he got out of a stint in rehab. Was there one moment you fell into it again? Was it one day? It's usually very gradual. You're standing at a precipice. And you lock down. And there's a little voice that says, jump. Just one. There's a voice that goes, jump. And the idea of just one. How hard was it to talk to your kids? Your wife? It's hard admitting. Once you've done that, it's easy. The sad thing is, you think that people don't notice. And you find out later on, we knew. Reporter: Williams had open-heart surgery to replace his aortic valve. A surgery that some have linked to depression. It is a risk factor that is looked at, postsurgically. You want to pay attention to folks that they're unable to engage the world. It kind of visits your mortality. Reporter: Williams discussed his own mortality with our Barbara Walters less than two years after his surgery. You said that the surgery was humbling. Totally. This is the big one. This is the one where they're dealing with the ticker, the main. The only other one more invasive is brain surgery. Reporter: It wasn't just health issues. Williams had stress in his personal life. He was device divorced. And was honest about the financial pain it caused. Telling "Parade" magazine, divorce is expensive. I used to joke they were going to call it all the money. But they changed it to alimony. It's ripping your heart out through your wallet. In that same interview, he said he was downsizing his life. And could no longer afford his 650-acre weekend estate in California's napa valley. He listed the villa of smiles for nearly $30 million, shortly before he died. The 20,000-square-foot 5-bedroom estate, features a home theater, tennis courts and beautiful views of the napa valley. And the home is still on the market. His professional life may have proved stressful, as well. Last year, he returned to TV once again for a CBS show called "The crazy one." Telling "Parade" magazine, the idea of having a steady job is appealing. But the show was canceled this past may, after just one season, due to poor ratings. The immense jimmy. Reporter: Robin Williams spent his final days in Marin county, just outside San Francisco, where the huge star was a seemingly regular guy. Nice to all of the neighbors. Really appreciated his kindness. I loved his sense of humor. I loved his -- the spontaneity of his life. Reporter: An avid cyclist, Williams had 100 bikes in his collection. He loved cycling. Reporter: He took them to this repair shop. The owner, Tony Tom, was Williams' close friend and biking partner. I'll miss him. Reporter: Tony said biking gave Williams some peace and tranquility. He came shortly after Tom belushi passed away from overdose. And he said cycling saved my life. And he says, biking is a whole lot better for you than cocaine. Mr. Williams? Reporter: But the legendary comedian and movie star was also known for championing the underdogs. Oh, look. It's showtime. Reporter: Using his star power to bring attention to issues like homelessness, in movies like "The fisher king." One more thing, never take your eye off the ball. Reporter: Even testifying on capitol hill about the issue. I've seen firsthand how homelessness affects children. Reporter: And his lasting work with the USO, lifting the spirits of 90,000 servicemen and women stationed overseas. When I come here, for you. Reporter: And across the country, landmarks that Williams made famous over the course of his storied career, are now memorials. That bench in Boston, from "Good will hunting." Now surrounded by tributes in chalk. That movie launched the careers of two unknowns, Ben Affleck and Matt Damon. And earned all three oscars. He made Matt and my dreams come true. What do you owe a guy that does that? Judging from the tributes of fans from all over the world, almost everyone felt they owed a lot to robin Williams. You don't know about real loss. That only occurs when you love something more than you love yourself. Reporter: In the end, perhaps Williams loved making his fans happy, more than he loved himself. But his loss is ours, as well. An epic talent. A lasting legacy.

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